Probing hydrogen under extreme conditions

April 13, 2012, Carnegie Institute
Probing hydrogen under extreme conditions
Periodic table detail of hydrogen by David Freund, courtesy iStockPhoto.

( -- How hydrogen--the most abundant element in the cosmos--responds to extremes of pressure and temperature is one of the major challenges in modern physical science. Moreover, knowledge gleaned from experiments using hydrogen as a testing ground on the nature of chemical bonding can fundamentally expand our understanding of matter. New work from Carnegie scientists has enabled researchers to examine hydrogen under pressures never before possible. Their work is published online in Physical Review Letters.

To explore in this new domain, the scientists developed new techniques to contain hydrogen at pressures of nearly 3 million times normal (300 Gigapascals) and to probe its bonding and with . They used a facility that Carnegie manages and operates at the National (NSLS) at Brookhaven National Laboratory in partnership with NSLS.

Observing hydrogen’s behavior under very high pressures has been a great challenge for researchers, because it is in a gas state under normal conditions. It is known that it has three solid molecular phases. But the structures and properties of highest-pressure phases are unknown.

For example, a transition to a phase that occurs at about 1.5 million times atmospheric pressure (150 Gigapascals) and at low temperatures has been of particular interest. But there have been technological hurdles in examining hydrogen at much higher pressures using static compression techniques.

It has been speculated that under at high pressures, hydrogen transforms to a metal, which means it conducts electricity. It could even become a superconductor or a superfluid that never freezes--a completely new and exotic state of matter.

In this new work, the research team, which included Carnegie’s Chang-sheng Zha, Zhenxian Liu, and Russell Hemley, developed new techniques to measure hydrogen samples at pressures above 3 million times normal atmospheric pressure (above 300 Gigapascals) and at temperatures ranging from -438 degrees Fahrenheit (12 Kelvin) to close to room temperature..

“These new static compression techniques have opened a window on the behavior of hydrogen at never-before-reached static pressures and temperatures,” said Hemley, director of the Geophysical Laboratory.

The team found that the molecular state was stable to remarkably high pressures, confirming extraordinary stability of the chemical bond between the atoms. Their work disproves the interpretations of experiments by other researchers reported last year indicating a metallic state under these conditions. Evidence for semimetallic behavior in the dense molecular phase was found in the new study, but the material must have electrical conductivity well below that of a full metal.

Meanwhile, in another paper also published in , a team from the University of Edinburgh and including Carnegie’s Alexander Goncharov report evidence for another phase of molecular hydrogen. They found it at the relatively high temperature of 80 degrees Fahrenheit (300 Kelvin) and under pressures above 220 Gigapascals. They suggest that the structure of hydrogen in this new phase is a honeycomb made of six-atom rings, similar to the carbon structure of graphene.

Explore further: On the path to metallic hydrogen

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1.5 / 5 (2) Apr 13, 2012
Electro-chemistry results in exotically extreme pressures. This could account for some of the cold fusion results (LENR). Other methods used are gas loading and plasma loading.
not rated yet Apr 13, 2012
I hope you meant the cold fusion remark as a possible way to explain the supposed excess energy (vs .. LOL .. fusion) ... and where do you see any mention of electro chemistry? I see EC as applicable to your comment on cold fusion as it is the basis of that whimsically named process. Some call it fusion, I call it chemistry .. usually producing nickle hydride and a bit of extra energy (more like a battery eh?). For the article ... they don't mention their compression/containment scheme at all. The only way to subject a sample to the 300 GPa pressure and temperatures mentioned ... AND (here's the important part), have enough time to actually analyze it, is with a diamond anvil.
not rated yet Apr 13, 2012
The only way that "cold fusion" could ever become real is if some exotic way was found to cancel or weaken the electrostatic repulsion of the nuclei involved. I suppose that that is not very likely, but think of the ray gun one could make if such a suppression field could be directed!
not rated yet Apr 13, 2012
That's just great. And for the longest time everyone was thinking of things to do with metallic hydrogen. Hah.

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